A signal processing apparatus includes a differential processing unit to differentiate a reflection signal corresponding to a pulse measurement beam that is periodically scanned in a polarized manner; an arithmetic unit to obtain, with a rising time of a first-order-differential reflection signal as a reference, a barycentric position of the first order differential reflection signal as a detection time of a reflected beam, and to calculate a distance to a measured object based on a time difference between an output time of the measurement beam and the detection time of the reflected beam; and a waveform determining unit to determine whether the reflected beam includes a plurality of overlapping reflected beams from a plurality of measured objects, based on rising and falling characteristics of the first-order-differential reflection signal and based on a rising characteristic of a second-order-differential reflection signal obtained by the second order differential of the reflection signal.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A signal processing apparatus configured to process a signal output from a rangefinder, the rangefinder comprising: a light emitting unit configured to output a pulse measurement beam to a measurement target space through an optical window; and a light receiving unit configured to detect a reflected beam reflected from a target measured object present in the measurement target space and to output a reflection signal corresponding to the reflected beam; the signal processing apparatus comprising: a differential processing unit configured to differentiate the reflection signal output from the light receiving unit; a waveform determining unit configured to determine whether the reflected beam includes a plurality of overlapping reflected beams reflected from a plurality of measured objects including the target measured object based on a rising characteristic and a falling characteristic of a first-order-differential reflection signal obtained by first order differential of the reflection signal by the differential processing unit and based on a rising characteristic of a second-order-differential reflection signal obtained by second order differential of the reflection signal by the differential processing unit; and an arithmetic unit configured to, in response to a determination of the waveform determining unit, calculate and output a distance to the target measured object based on the reflection signal.
2. The signal processing apparatus according to claim 1 , wherein when the waveform determining unit detects a second rise time or the subsequent rise time on the second-order-differential reflection signal that is raised to or beyond a predetermined threshold value by a time the first-order-differential reflection signal falls to or below a predetermined threshold value, the waveform determining unit is configured to determine that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects including the target measured object.
3. The signal processing apparatus according to claim 1 , wherein the arithmetic unit is configured to calculate a barycentric position of the first-order-differential reflection signal obtained by first order differential by the differential processing unit, to obtain a time corresponding to the barycentric position as a detection time of the reflected beam, and to calculate a distance to the target measured object based on a time difference between an output time of the measurement beam and the detection time of the reflected beam.
4. The signal processing apparatus according to claim 1 , wherein when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects, the arithmetic unit is configured to output a signal indicating that the optical window is unclear and contaminated.
5. The signal processing apparatus according to claim 1 , wherein the waveform determining unit is configured to determine that when a ratio P/W of a peak value P to a pulse width W with respect to the reflected beam is lower than a predetermined threshold value Pb/Wb, the reflected beam is not appropriate, and wherein when the waveform determining unit determines that the reflected beam is not appropriate, the arithmetic unit is configured to stop calculation of the distance or stop output of the calculated distance.
6. A signal processing apparatus configured to process a signal output from a rangefinder, the rangefinder comprising: a light emitting unit configured to output a pulse measurement beam to a measurement target space through an optical window; and a light receiving unit configured to detect a reflected beam reflected from a target measured object present in the measurement target space and to output a reflection signal corresponding to the reflected beam; the signal processing apparatus comprising: a differential processing unit configured to differentiate the reflection signal output from the light receiving unit; a waveform determining unit configured to determine whether the reflected beam includes a plurality of overlapping reflected beams reflected from a plurality of measured objects including the target measured object based on a rising characteristic and a falling characteristic of a first-order-differential reflection signal obtained by first order differential of the reflection signal by the differential processing unit and based on a rising characteristic of a second-order-differential reflection signal obtained by second order differential of the reflection signal by the differential processing unit; a signal separating unit configured to separate the reflection signal with reference to a second rise time or the subsequent rise time on the second-order-differential reflection signal when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects; and an arithmetic unit configured to calculate a barycentric position of the first-order-differential reflection signal for the reflection signal separated by the signal separating unit with reference to the second rise time or the subsequent rise time on the second-order-differential reflection signal, to obtain a time corresponding to the barycentric position as a detection time of the reflected beam, and to calculate and output a distance to the target measured object based on a time difference between an output time of the measurement beam and the detection time of the reflected beam.
7. The signal processing apparatus according to claim 6 , further comprising a memory storing correction data to correct a distance calculated with reference to the second rise time or the subsequent rise time on the second-order-differential reflection signal, with regard to a reference reflected beam including a plurality of overlapping reflected beams reflected from a plurality of measured objects whose relative position is predetermined, based on a relation among a distance calculated with reference to a rise time of a first-order-differential reflection signal, a distance calculated with reference to a second rise time or the subsequent rise time on a second-order-differential reflection signal of the reference reflected beam, and peak values of reflection signals targeted for calculation of each of the distances related to the reference reflected beam, and wherein the arithmetic unit is configured to correct the distance calculated with reference to the second rise time or the subsequent rise time on the second-order-differential reflection signal based on the correction data stored in the memory.
8. The signal processing apparatus according to claim 6 , wherein when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects, the arithmetic unit is configured to output a distance calculated based on a reflection signal showing a maximum peak value among reflection signals separated by the signal separating unit as the distance to the target measured object.
9. The signal processing apparatus according to claim 6 , wherein when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects, the arithmetic unit is configured to output a signal indicating that the optical window is unclear and contaminated.
10. The signal processing apparatus according to claim 6 , wherein the waveform determining unit is configured to determine that when a ratio P/W of a peak value P to a pulse width W with respect to the reflected beam is lower than a predetermined threshold value Pb/Wb, the reflected beam is not appropriate, and wherein when the waveform determining unit determines that the reflected beam is not appropriate, the arithmetic unit is configured to stop calculation of the distance or stop output of the calculated distance.
11. A signal processing apparatus configured to process a signal output from a rangefinder, the rangefinder comprising: a light emitting unit configured to output a pulse measurement beam to a measurement target space through an optical window; and a light receiving unit configured to detect a reflected beam reflected from a target measured object present in the measurement target space and to output a reflection signal corresponding to the reflected beam; the signal processing apparatus comprising: a differential processing unit configured to differentiate the reflection signal output from the light receiving unit; a waveform determining unit configured to determine whether the reflected beam includes a plurality of overlapping reflected beams reflected from a plurality of measured objects including the target measured object based on a rising characteristic and a falling characteristic of a first-order-differential reflection signal obtained by first order differential e of the reflection signal by the differential processing unit and based on a rising characteristic of a second-order-differential reflection signal obtained by second order differential of the reflection signal by the differential processing unit; and an arithmetic unit configured to, in response to a determination of the waveform determining unit, calculate a distance to the target measured object based on the reflection signal, and to output the distance only when the distance calculated for the measurement beam scanned in a deflected manner by a scanning unit in one same direction falls within a predetermined allowable range in a plurality of periods.
12. The signal processing apparatus according to claim 11 , wherein when the waveform determining unit detects a second rise time or the subsequent rise time on the second-order-differential reflection signal that is raised to or beyond a predetermined threshold value by a time the first-order-differential reflection signal falls to or below a predetermined threshold value, the waveform determining unit is configured to determine that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects including the target measured object.
13. The signal processing apparatus according to claim 11 , wherein the arithmetic unit is configured to calculate a barycentric position of the first-order-differential reflection signal obtained by first order differential by the differential processing unit, to obtain a time corresponding to the barycentric position as a detection time of the reflected beam, and to calculate a distance to the target measured object based on a time difference between an output time of the measurement beam and the detection time of the reflected beam.
14. The signal processing apparatus according to claim 11 , wherein when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects, the arithmetic unit is configured to output a signal indicating that the optical window is unclear and contaminated.
15. The signal processing apparatus according to claim 11 , wherein the waveform determining unit is configured to determine that when a ratio P/W of a peak value P to a pulse width W with respect to the reflected beam is lower than a predetermined threshold value Pb/Wb, the reflected beam is not appropriate, and wherein when the waveform determining unit determines that the reflected beam is not appropriate, the arithmetic unit is configured to stop calculation of the distance or stop output of the calculated distance.
16. The signal processing apparatus according to claim 11 , further comprising a signal separating unit configured to separate the reflection signal with reference to a second rise time or the subsequent rise time on the second-order-differential reflection signal when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects, wherein the arithmetic unit is configured to calculate a barycentric position of the first-order-differential reflection signal for the reflection signal separated by the signal separating unit with reference to the second rise time or the subsequent rise time on the second-order-differential reflection signal, to obtain a time corresponding to the barycentric position as the detection time of the reflected beam, and to calculate the distance to the target measured object based on a time difference between an output time of the measurement beam and a detection time of the reflected beam.
17. The signal processing apparatus according to claim 11 , wherein further comprising a memory storing correction data to correct a distance calculated with reference to the second rise time or the subsequent rise time on the second-order-differential reflection signal, with regard to a reference reflected beam including a plurality of overlapping reflected beams reflected from a plurality of measured objects whose relative position is predetermined, based on a relation among a distance calculated with reference to a rise time of a first-order-differential reflection signal, a distance calculated with reference to a second rise time or the subsequent rise time on a second-order-differential reflection signal of the reference reflected beam, and peak values of reflection signals targeted for calculation of each of the distances related to the reference reflected beam, and wherein the arithmetic unit is configured to correct the distance calculated with reference to the second rise time or the subsequent rise time on the second-order-differential reflection signal based on the correction data stored in the memory.
18. The signal processing apparatus according to claim 11 , wherein when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects, the arithmetic unit is configured to output a distance calculated based on a reflection signal showing a maximum peak value among reflection signals separated by the signal separating unit as the distance to the target measured object.
19. The signal processing apparatus according to claim 11 , wherein when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects, the arithmetic unit is configured to output a signal indicating that the optical window is unclear and contaminated.
20. The signal processing apparatus according to claim 11 , wherein the waveform determining unit is configured to determine that when the ratio P/W of the peak value P to the pulse width W with respect to the reflected beam is lower than the predetermined threshold value Pb/Wb, the reflected beam is not appropriate, and wherein when the waveform determining unit determines that the reflected beam is not appropriate, the arithmetic unit is configured to stop calculation of the distance or stop output of the calculated distance.
21. A scanning rangefinder comprising: a light emitting unit configured to output a pulse measurement beam; a scanning unit to periodically scan the measurement beam output from the light emitting unit in a deflected manner to a measurement target space through an optical window; a light receiving unit configured to detect a reflected beam including a plurality of overlapping reflected beams reflected from a plurality of measured objects including a target measured object present in the measurement target space, and to output a reflection signal corresponding to the reflected beam; and the signal processing apparatus configured to process the reflection signal output from the light receiving unit and to calculate and output a distance to the target measured object, the signal processing apparatus including: a differential processing unit configured to differentiate the reflection signal output from the light receiving unit; a waveform determining unit configured to determine whether the reflected beam includes a plurality of overlapping reflected beams reflected from a plurality of measured objects including the target measured object based on a rising characteristic and a falling characteristic of a first-order-differential reflection signal obtained by first order differential of the reflection signal by the differential processing unit and based on a rising characteristic of a second-order-differential reflection obtained by second order differential of the reflection signal by the differential processing unit; and an arithmetic unit configured to, in response to a determination of the waveform determining unit, calculate and output a distance to the target measured object based on the reflection signal.
22. A scanning rangefinder comprising: a light emitting unit configured to output a pulse measurement beam; a scanning unit to periodically scan the measurement beam output from the light emitting unit in a deflected manner to a measurement target space through an optical window; a light receiving unit configured to detect a reflected beam including a plurality of overlapping reflected beams reflected from a plurality of measured objects including a target measured object present in the measurement target space, and to output a reflection signal corresponding to the reflected beam; and the signal processing configured to process the reflection signal output from the light receiving unit, and to calculate and output a distance to the target measured object, the signal processing apparatus including: a differential processing unit configured to differentiate the reflection signal output from the light receiving unit: a waveform determining unit configured to determine whether the reflected beam includes a plurality of overlapping reflected beams reflected from a plurality of measured objects including the target measured object based on a rising characteristic and a falling characteristic of a first-order-differential reflection signal obtained by first order differential of the reflection signal by the differential processing unit and based on a rising characteristic of a second-order-differential reflection signal obtained by second order differential of the reflection signal by the differential processing unit; a signal separating unit configured to separate the reflection signal with reference to a second rise time or the subsequent rise time on the second-order-differential reflection signal when the waveform determining unit determines that the reflected beam includes the plurality of overlapping reflected beams reflected from the plurality of measured objects; and an arithmetic unit configured to calculate a barycentric position of the first-order-differential reflection signal for the reflection signal separated by the signal separating unit with reference to the second rise time or the subsequent rise time on the second-order-differential reflection signal, to obtain a time corresponding to the barycentric position as a detection time of the reflected beam, and to calculate and output a distance to the target measured object based on a time difference between an output time of the measurement beam and the detection time of the reflected beam.
23. A scanning rangefinder comprising: a light emitting unit configured to output a pulse measurement beam; a scanning unit to periodically scan the measurement beam output from the light emitting unit in a deflected manner to a measurement target space through an optical window; a light receiving unit configured to detect a reflected beam including a plurality of overlapping reflected beams reflected from a plurality of measured objects including the target measured object present in the measurement target space, and to output a reflection signal corresponding to the reflected beam; and the signal processing apparatus configured to process the reflection signal output from the light receiving unit, and to calculate and output a distance to the target measured object, the signal processing apparatus including: a differential processing unit configured to differentiate the reflection signal output from the light receiving unit; a waveform determining unit configured to determine whether the reflected beam includes a plurality of overlapping reflected beams reflected from a plurality of measured objects including the target measured object based on a rising characteristic and a falling characteristic of a first-order-differential reflection signal obtained by first order differential of the reflection signal by the differential processing unit and based on a rising characteristic of a second-order-differential reflection signal obtained by second order differential of the reflection signal by the differential processing unit; and an arithmetic unit configured to in response to a determination of the waveform determining unit, calculate a distance to the target measured object based on the reflection signal, and to output the distance only when the distance calculated for the measurement beam scanned in a deflected manner by a scanning unit in one same direction falls within a predetermined allowable range in a plurality of periods.
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March 30, 2011
September 9, 2014
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